Tyre sensor interrogation and valve therefore

ABSTRACT

A system for interrogating a tire sensor. The disclosure provides a wheel ( 2 ) including a sensor ( 14 ) and an electrical conductor ( 18, 20 ) extending about a rotational axis ( 4 ) of the wheel ( 2 ), the sensor ( 14 ) being electrically coupled to said electrical conductor ( 18, 20 ). Communication between the sensor and a remote interrogating apparatus is thereby improved.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a system for interrogating a tiresensor.

DESCRIPTION OF RELATED ART

It is known to monitor the characteristics of a tire through use of oneor more Surface Acoustic Wave (SAW) sensors. Such sensors are generallymounted inside the tire and are electrically connected to an antenna byvirtue of which signals may be communicated between the sensor and aremote transmitter/receiver. A problem associated with this prior artsystem is that, as the tire rotates in use, the sensor and associatedantenna also rotate. Accordingly, the position of the sensor and antennarapidly oscillates relative to the position of the transmitter/receiverand this can complicate interpretation of signals transmitted betweenthe sensor and transmitter/receiver.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a wheel comprising asensor electrically coupled to an electrical conductor within thestructure of the wheel. The sensor may be a SAW sensor. The sensor maybe capacitively coupled to the electrical conductor. The electricalconductor may be a rim of the wheel and/or elements within a tiremounted on the wheel. The tire elements may be reinforcing componentswithin the tire. The tire elements may, for example, be a metal rim orbraid. Furthermore, the sensor may be electrically coupled to theelectrical conductor by means of a dipole or antenna. The dipole/antennais preferably positioned within the wheel so as to excite anelectromagnetic wave travelling around the wheel. The antenna may be ahelical antenna.

A second aspect of the present invention provides a valve for a tire,wherein the valve comprises a sensor and dipole or antenna, wherein thedipole or antenna is electrically coupled to both the sensor and a bodyof the valve. The body of the valve is preferably metallic and adaptedfor connection with a wheel rim. Said connection may be an electricalconnection.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described withreference to the accompanying drawings, in which:

FIG. 1 is a first embodiment of the present invention;

FIG. 2 is a second embodiment of the present invention;

FIG. 3A is a side view of a valve body for use in connection with thepresent invention;

FIG. 3B is a cross-sectional side view of the valve body shown in FIG.3A;

FIG. 3C is an end view of the valve body shown in FIG. 3A;

FIG. 4A is a side view of a further valve body for use in connectionwith the present invention;

FIG. 4B is a cross-sectional side view of the valve body shown in FIG.4A;

FIG. 4C is an end view of the valve body shown in FIG. 4A; and

FIG. 5 is a cross-sectional partial view of a wheel according to thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A wheel 2 according to the present invention is shown in FIG. 5 of theaccompanying drawings. The wheel 2 is shown in cross-section takenthrough a plane in which a rotational axis 4 of the wheel 2 lies. As thewheel 2 is symmetrical about the rotational axis 4, only the portion ofwheel 2 located above the rotational axis 4 is shown in FIG. 5. Theconstruction of a conventional automobile wheel will be well known tothose skilled in the art and a detailed description thereof will not benecessary. Nevertheless, for the sake of completeness, it will beunderstood that the wheel 2 shown in FIG. 5 comprises a wheel hub 6 uponwhich a pneumatic tire 8 is mounted. A valve 10 extends through anaperture in the wheel hub 6 so as to allow air to be forced into thecavity 12 between the tire 8 and the hub 6. The valve 10 has a one-waycharacteristic so that air maybe admitted into the cavity 12 withoutbeing released therefrom (unless a release mechanism within the valve isactivated). The tire 8 may be thereby conveniently inflated on the wheelhub 6.

In accordance with the present invention, the valve 10 is provided witha sensor (such as a SAW sensor) for monitoring characteristics such astire pressure and temperature. A SAW sensor 14 is shown in FIG. 5located in a slot defined in the body of the valve 10. The sensor 14 iselectrically connected to a helical antenna 16 which itself ismechanically mounted to the body of the valve 10. The antenna 16 islocated sufficiently close to the rim 18 of the hub 6 and thereinforcing elements 20 located within the tire side wall to induce anelectro-magnetic wave therein. The antenna 16 may be locatedsufficiently close to the rim 18 and/or the reinforcing elements 20 sothat the rim 18 and/or elements 20 lie within the near magnetic fieldgenerated by the antenna 16 when the sensor 14 activates.

Only some of the reinforcing elements 20 of the tire 8 are shown in FIG.5 and those that are shown are illustrated in a schematic manner. Areader skilled in the art will be familiar with the arrangement of thereinforcing elements 20 in a pneumatic automobile tire.

An enlarged view of the valve 10 is shown in FIG. 2 of the accompanyingdrawings. As an alternative to the valve 10, the valve 30 shown in FIG.1 of the accompanying drawings may be mounted to the wheel hub 6. Itwill be seen with reference to FIG. 1 that, rather than mounting the SAWsensor in a slot as in the case of the valve 10 shown in FIG. 2, thevalve 30 shown in FIG. 1 comprises a SAW sensor 32 secured to the valvebody 34 by means of a mounting bracket 36. The valve 30 of FIG. 1 alsocomprises a helical antenna 38 secured to the valve body 34 andelectrically connected to the sensor 32.

With particular reference to FIGS. 1 and 2 it will be seen that in thecase of each valve 30,10 a helical antenna 38 (or, alternatively, ashort dipole) is mechanically attached to a valve and electricallyconnected to a SAW sensor. The location of the antenna/dipole and sensoris such that, when the valve is secured to a wheel, the antenna/dipoleand sensor are located inside a tire mounted on the wheel rim. Oneterminal of the sensor is also connected to a metal body of the valve.In this way, the valve body may be employed as an RF “counterweight”.Each valve may be capacitively coupled to a wheel rim. Thedipole/antenna is positioned inside the tire in such a way that itexcites an electro-magnetic wave which travels around the tire as aresult of reflections from the metal wheel rim and tire braid.Effectively, the tire operates as an electro-magnetic waveguide andspreads an electro-magnetic field across the whole tire. Accordingly,the tire walls radiate the electromagnetic wave around the wholecircumference of the wheel. This is in contrast to use of a conventionalantenna which operates as a point source. In the present invention, theentire wheel effectively operates as an antenna. This increases thesector within which a sensor can be excited by an interrogation pulseand considerably simplifies the interrogation process.

In the valve 30 of FIG. 1, the SAW sensor is mounted to the valve bymeans of a mounting bracket. However, in the valve 10 of FIG. 2, the SAWsensor is mounted directly on the valve body. Valve bodies suitable fordirectly receiving a sensor are illustrated in FIGS. 3 and 4 of theaccompanying drawings. Each of the valve bodies 50,60 shown in FIGS. 3and 4 respectively define a slot 52,62 in which a sensor may be located.Each slot 52,62 is defined in the associated valve body so as to cutacross the air passageway 54,64 through which, in use, inflation air isadmitted into the tire cavity 12 (see FIG. 5). In this way, when thesensor is located in the slot, inflation air passing through the valvepasses around the sensor. The sensor is thereby exposed to the inflationair and may monitor the characteristics thereof. The slot 52,62 is alsoprovided in that portion of the valve body which remains located withinthe tire cavity 12. In this way, the sensor may also monitor thecharacteristics of the air within the tire during a normal use of theassociated wheel.

The present invention is not limited to the specific embodimentsdescribed above. Alternative arrangements will be apparent to thoseskilled in the art.

1. A wheel (2) comprising a tire (8) and a hub (6) on which the tire (8)is mounted so as to define a cavity (12) therebetween; and an electricalconductor (20) extending about a rotational axis (4) of the wheel (2);the wheel (2) further comprising a sensor (14), and an antenna (16)located in the cavity (12) and associated with the sensor (14), thesensor (14) and antenna (16) being adapted to operate in combinationwith one another so as to radiate an electro-magnetic wave of such awavelength that said electro-magnetic wave is reflected by theelectrical conductor (20) and thereby propagates within the cavity (12)about the rotational axis (4); wherein the antenna (16) is orientedwithin the cavity (12) so that force lines of a near electro-magneticfield associated with the antenna (16) align with force lines of theelectro-magnetic wave.
 2. A wheel (2) as claimed in claim 1, wherein theantenna (16) is oriented so as to extend radially relative to therotational axis (4).
 3. A wheel (2) as claimed in claim 1, wherein theantenna (16) comprises a dipole or helical antenna.
 4. A wheel (2) asclaimed in claim 3, wherein the antenna is oriented along the forcelines of the electro-magnetic wave.
 5. A wheel (2) as claimed in claim1, wherein the antenna (16) is physically connected to the sensor (14).6. A wheel (2) as claimed in claim 1, wherein the antenna (16) ismounted on a tire valve (10).
 7. A wheel (2) as claimed in claim 1,wherein the sensor (14) is mounted to a tire valve (10).
 8. A wheel (2)as claimed in claim 1, wherein the sensor (14) is a Surface AcousticWave sensor.
 9. A wheel (2) as claimed in claim 1, wherein the antenna(16) is positioned relative to the electrical conductor (20) so thatsaid conductor (20) lies within the near electro-magnetic fieldassociated with the antenna (16) when the sensor (14) activates.
 10. Awheel (2) as claimed in claim 1, wherein the electrical conductor (20)circumscribes the rotational axis (4) of the wheel (2).
 11. A wheel (2)as claimed in claim 1, wherein the electrical conductor (20) comprises aload bearing component of the wheel (2).
 12. A wheel (2) as claimed inclaim 1, wherein the electrical conductor (20) comprises a tiresupporting surface of the wheel (2).
 13. A wheel (2) as claimed in claim1, wherein the electrical conductor (20) comprises a circumferentialtire retaining rim (18).
 14. A wheel (2) as claimed in claim 1, whereinthe electrical conductor (20) comprises an element within the tire (8).15. A wheel (2) as claimed in claim 14, wherein said tire element is atire reinforcing component.
 16. A wheel (2) as claimed in claim 14,wherein said tire element is a metal rim or braid.